The banning of steel-string guitars in British prisons has come under fire from a group of prominent musicians, including Billy Bragg, Johnny Marr, Dave Gilmour and Richard Hawley.

In a letter published in the Guardian, the 12 signatories urge the minister for justice, Chris Grayling, to overturn the blanket ban on the instruments, which they believe undermines the important role music has to play in "engaging prisoners in the process of rehabilitation".

The ban came in as part of the government's changes to the incentive and earned privileges policy for prisoners in November last year, the same initiatives that banned prisoners from receiving books. Nylon stringed guitars are still allowed for those who earn the privilege.

The letter goes on to state: "As most guitars currently owned or used by inmates in our prisons are steel-strung acoustics, this ruling will mean that these instruments are kept under lock and key until time for a supervised session, if the prison in question has provision for musical tuition."

The issue will be raised on Tuesday in parliament by Labour MP Kevin Brennan, who said he found the ban baffling and wanted to "try to find some answers".

"When some prisoners wrote to me about how they saved from their prison wages to buy guitars which were now being banned I thought the government would have some genuine reason for this change," he said. "The prisons minister has admitted that learning the guitar is good for rehabilitation so why he would want to undermine rehabilitation by this arbitrary policy on guitar strings is baffling."

Bragg, who runs the not-for-profit initiative Jail Guitar Doors, which provides musical instruments for prisons, said it was part of a disturbing trend.

"Of the 350-odd instruments we have given to prisons since I began the Jail Guitar Doors initiative, almost all have been been steel-strung guitars," he said.

"I've seen the positive impact giving prisoners these guitars can have first hand, which is why I am involved in this issue. There's never been to my knowledge, an incident in a British prison where someone has been attacked with a steel string guitar. It makes no sense – where's the logic behind this? Where's the thinking behind this?

"Almost all the guitars currently in British prisons tend to be steel strung, so this effectively means they've all been removed as it's just not possible to re-string them all with nylon. They aren't designed for that.

"These guitars allows the prisoners to develop their skills and do peer to peer work which has been shown as really important as the basis for rehabilitation. A number of prison staff have told me that that aspect of them sitting down together, playing music and learning, has had a noticeable impact on individual prisoners and the atmosphere as a whole.

"It's not about vocation, it's about incentivising prisoners to engage in rehabilitation. Surely that's one of the most important things a prison can do?" Bragg said. "Can they not see that this move has real ramifications?"

Andrew Nielson, director of campaigns at the Howard League for Penal Reform, echoed Bragg's sentiments and said they would be "very much" supporting Brennan's debate in parliament.

He said: "We feel that this is a petty move which does undermine the government's stated in intention of seeing prisons as purposeful places where rehabilitation is a priority. It seems to me to be symptomatic of a careless attitude towards policy making"

Other musicians that have signed the letter include Seasick Steve, Speech Debelle, and Scroobius Pip.

A Prison Service spokesperson said: "As a result of this government's reforms, prisoners who do not engage with their own rehabilitation now have far fewer privileges."